This invention relates to machines for making chips from brushwood and the like. These are used by tree surgeons, contractors, and public authorities, to clear waste timber and turn it into a particulate material useful for mulching, compost production, and possibly as a material for making wood-based products such as chip-board.
The industry standard machine has a feed roller or rollers provided with teeth to grip and embed in the branches, small diameter logs, twigs and the like, and feed these through a throat to meet a flywheel generally at a radial position relative to its center. The flywheel is massive because of the requirements, and carries cutter blades on one face at a plurality of radial locations, typically three, each of which is a straight blade which has its cutting edge extending parallel to an individual radius of the flywheel and of a length corresponding to a particular dimension of the throat. One edge of the throat provides a second cutting edge. As each blade moves over the throat and across the second cutting edge, the end of the fed material, which projects beyond that edge, is impacted by the blade and chopped off Because of the nature of the material with a grain structure, a large area, as of a log, is fractured into a large number of chips. Small cross-sectional areas such as twigs may form only a single chip with each cutting stroke.
The flywheel may rotate at a high speed on the order of hundreds or thousands of RPM, and there is considerable noise from the cutters operation as well as from the driving source. The blade life is relatively short between each re-sharpening operation or replacement, due to ordinary wear and tear, and to foreign bodies which tend to be fed in, e.g., stones or grit. In ordinary operations, a chipper run more-or-less continuously during working shifts may need sharpening every 15-30 hours, and can be re-sharpened a limited number of times.
The object of the invention is to provide improvements, particularly in shortening down-time when sharpening is called for, in reducing cost of re-sharpening, and in reducing the cost of replacement blades. Supplementary objects include reducing noise and power requirements.